This demo apparently originates from the Computer Gaming World CD #156 (July 1997). I have no idea if Rowan released any downloadable demo of the same game - original distributions of their stuff are all quite hard to find!

Most other packages I found at cd.textfiles.com are incomplete (apparently whoever zipped them forgot to add commands to recurse subdirectories and add contents), making the demo versions unplayable. The one I linked to in my previous post does work though, but it's very clearly not the original thing, and it also lacks the non-interactive demo of The Battle of Britain.